CA ERFO KLAMATH NF 18N31(1) Final Pavement Memo.pdf

Memorandum

Subject: CA ERFO KLAMATH NF 18N31(1)

Upper West Branch Bridge Final Pavement Recommendations

Date: January 14, 2022

From: Robert Norick

Through:

Pavement & Materials Engineer

Mike Voth Pavement & Materials Team Lead

To: Mike Daigler, PM Paul Aguilar, Lead Designer

Project Description:

This memorandum provides the pavement structural section recommendations for the CA ERFO KLAMATH NF 18N31(1) Upper West Branch Bridge in Sisikiyou County, California. The bridge is located approximately 12.5 miles northwest of the Town of Happy Camp along Forest Route 18N31 within the Klamath National Forest and crosses the West Branch of Indian Creek (see vicinity map that follows). The bridge was completely damaged by fire in 2020 and will be fully replaced with a proposed concrete bridge with wood cellulose nanocrystals incorporated into the precast concrete girders.

The original bridge was constructed in 1966 and was a one-lane, two-way traffic, treated timber bridge. The existing bridge is 79.0 feet long with a lane width of 11.0 feet and a deck width of 15.0 feet.

Geotechnical Investigation:

In June 2021, CFL’s Geotechnical Group conducted a geotechnical investigation for the project consisting of two 30-foot deep geotechnical borings (one at each bridge abutment) using a truck mounted hollow stem auger. Standard penetration tests (SPT) and sampling was performed at both borings at 5-foot intervals. CFL personnel logged the findings including depth of boring and subgrade soils, SPT data, visual soil classification, and aggregate base thicknesses. SPT subgrade samples were collected and submitted to the CFLHD lab for testing to determine the soil classifications. The geotechnical investigation found 6 inches of aggregate base over a silty sand subgrade;

“good” quality subgrade material. Based upon Exhibits 11.4.2.B and 11.4.2.C of CFLHD’s supplement to the PDDM, the resilient modulus (MR) of “good” subgrade soils can be estimated to be 8,000 psi.

ROBERT E NORICK Digitally signed by ROBERT E NORICK

Date: 2022.01.14 11:48:44 -07'00'

Pavement Recommendations:

The two-way average daily traffic (ADT) along the forest routes are estimated to be less than 100 with a minimal number of trucks; i.e. a “low” traffic level. According to PDDM Section 11.2.1.2, a minimum of 50,000 ESALs shall be used for the design of paved roads. Based upon 50,000 ESALs, the subgrade resilient moduli (MR), and the PDDM pavement design criteria, the 1993 AASHTO procedure requires a 20-year pavement Structural Numbers (SN) of 1.85. After evaluating alternatives, the following pavement structural sections are recommended for the project.

Upper West Branch Bridge Deck

2 inch asphalt over waterproofing membrane over precast concrete girders

Upper West Branch Bridge Approaches (SN = 1.92)

3 inches of Asphalt Concrete Pavement (SN = 3” x 0.44 = 1.32”) 6 inches of Crushed Aggregate Base (SN = 6” x 0.10 = 0.60”)

Recommended Pay Items:

Item Number Item Description Unit

30202-2000 Roadway Aggregate, Method 2 Ton 40301-0100 Asphalt Concrete Pavement, Type 1 Ton

Recommended SCRs:

CFLHD standard SCRs related to pavements and materials are expected to be used with the exception of SCRs for FP-14 Sections 403, 552, and 553 (see attached). For the 403 SCR, Subsection 403.01 and Table 403-1 have been modified to incorporate Caltrans 85 gyration asphalt mixes. At the request of the Forest Service and to support the evaluation of new materials, 552 and 553 SCRs have been developed for the use of wood cellulose nanocrystals for the precast concrete girders. Research has shown that the cement content of concrete mixes can be reduced with the use of wood cellulose nanocrystals, thus creating a more environmentally friendly concrete mix. The Government will provide the cellulose nanocrystal additive. The precast concrete mix will start with the precaster’s standard mix and then add the cellulose nanocrystals and reduce cement content accordingly. Special contract requirements are necessary for incorporating cellulose nanocrystals into the concrete mix design, as well as, for the storage and mixing of the nanocrystals.

Vicinity Map